Add DataRows to a Combobox in VB.NET without using data binding

You can bind a DataTable to a Combobox to display one value in the ComboBox's list while using another value to identify rows. VB6 provided the ItemData property for this purpose. .NET did away with the ItemData property but allows you to bind almost any type of data object to a ComboBox. My Bind Combobox page illustrates how to do bind a DataTable to a ComboBox.

However, a bug exists in the .NET Framework V1.1 (see article Q327244) when the ComboBox is used on a Tab Control. The bug causes the ComboBox to select its first item when the tab control's selected index changes. Also, the ComboBox cannot be cleared unless its SelectedIndex property is set to -1 twice. click here to learn how to get around this.

This page shows how to add DataRow values to ComboBox without using data binding. When you want to look up the ComboBox's display value based on a second DataRow value there is more manual work since there is no binding but it always works.

Retrieve the data into a DataSet:

    Dim strSQL As String = "Select Code,Description From MyTable"
    Dim Connection As New OleDbConnection("PROVIDER=....")
    Dim DA As New OleDbDataAdapter(strSQL, Connection)
    Dim DS As New DataSet

    DA.Fill(DS, "Codes")

Populate the ComboBox:

    Dim dt As New DataTable = DS.Tables(0)
    Dim dr As DataRow
    '
    ' Populate the Combobox with the Descriptions.
    '
    For Each dr In dt.Rows()
       cbo.Items.Add(dr("Description"))
    Next
    cbo.SelectedIndex = -1

To select a Description based on a "Code":

    Dim intCBOIndex As Integer = -1

    intCBOIndex = GetComboBoxIndexFromValue(cbo, dt, dr("Code"), 1)
    cbo.SelectedIndex = intCBOIndex 

    Private Function GetComboBoxIndexFromValue( _
    ByVal theCBO As ComboBox, _
    ByVal theDataTable As DataTable, _
    ByVal theValue As Object, _
    ByVal theValueColumn As Integer) As Integer
    '
    ' Return the index of the ComboBox item whose associated
    ' data value matches the passed in value. Data values ARE 
    ' NOT stored in the Combox.
    '
    Try
        '
        ' If the value to look for is blank, get out.
        '
        Dim strValue As String = theValue.ToString.Trim
        If strValue = "" Then Return -1
        '
        ' Data values are stored in a DataTable. Filter the datatable 
        ' to find the row containing the value we are looking for.
        '
        Dim strDisplayValue As String
        Dim strFilter As String

        If theDataTable.Columns(theValueColumn).DataType _
              Is System.Type.GetType("System.String") Then
            strFilter = theDataTable.Columns(theValueColumn).ColumnName & "='" & strValue & "'"
        Else
            strFilter = theDataTable,Columns(theValueColumn).ColumnName & "=" & strValue
        End If
        theDataTable.DefaultView.RowFilter = strFilter
        '
        ' Get the Display value from the datarow and find it in the ComboBox.
        '
        If theDataTable.DefaultView.Count = 0 Then
            Return -1
        Else
            strDisplayValue = theDataTable.DefaultView(0)("DESCRIPTION").ToString()
            theDataTable.DefaultView.RowFilter = ""
            Return theCBO.FindStringExact(strDisplayValue)
        End If

        Catch ex As Exception
            MessageBox.Show(....)
        End Try

    End Function


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